Polycrystalline abrasive materials and method of manufacture

Abstract

A method of manufacturing polycrystalline abrasive elements consisting of micron, sub-micron or nano-sized ultrahard abrasives dispersed in micron, sub-micron or nano-sized matrix materials. A plurality of ultrahard abrasive particles having vitreophilic surfaces are coated with a matrix precursor material and then treated to render them suitable for sintering. The matrix precursor material can be converted to an oxide, nitride, carbide, oxynitride, oxycarbide, or carbonitride, or an elemental form thereof. The coated ultrahard abrasive particles are consolidated and sintered at a pressure and temperature at which they are crystallographically or thermodynamically stable.

The invention claimed is: 
     
       1. A method of manufacturing a polycrystalline abrasive element including the steps of
 providing a plurality of ultrahard micron, sub-micron or nano size abrasive particles having vitreophilic surfaces that form chemical bonds with oxides, 
 coating the ultrahard abrasive particles with an amorphous or nano-crystalline oxide, hydroxide or oxo-hydroxide matrix precursor material using a wet colloidal suspension reaction method, 
 heating the coated ultrahard abrasive particles to dry the coating, and 
 heating the coated ultrahard abrasive particles in a gaseous environment to convert the matrix precursor coating material to an oxide, nitride, carbide, oxynitride, oxycarbide and/or carbonitride of the matrix precursor material, or an element form of the matrix precursor material, or combinations thereof; and 
 consolidating and sintering the coated ultrahard abrasive particles at a pressure and temperature at which they are crystallographically or thermodynamically stable to generate a polycrystalline abrasive element comprising ultrahard abrasive particles or grains of sub-micron or nano size in the matrix material. 
 
     
     
       2. A method according to  claim 1 , wherein the ultrahard abrasive particles are selected from the group comprising diamond, cubic boron nitride, silicon carbide, silicon nitride, boron carbide and boron suboxide (B 6 O). 
     
     
       3. A method according to  claim 1 , wherein the ultrahard abrasive particles are diamond or cubic boron nitride or a combination of these materials, and wherein the particles are treated in a surface treatment process in order to render the surfaces thereof vitreophilic. 
     
     
       4. A method according to  claim 1 , wherein the converted matrix precursor material is selected from micron, sub micron or nano-grain sized oxides, nitrides, carbides, oxynitrides, oxycarbides and carbonitrides of the matrix precursor materials, or elemental matrix precursor materials, or combinations thereof. 
     
     
       5. A method according to  claim 1 , wherein the converted matrix precursor material is selected from the oxides, nitrides, carbides, oxynitrides, oxycarbides and carbonitrides of aluminium, titanium, silicon, vanadium, zirconium, niobium, hafnium, tantalum, chromium, molybdenum and tungsten and any appropriate combination of these materials. 
     
     
       6. A method according to  claim 1 , wherein the matrix precursor material is an amorphous or nano-grain sized compound of aluminium, titanium, silicon, vanadium, zirconium, niobium, hafnium, tantalum, chromium, molybdenum and tungsten and any appropriate combination of these materials. 
     
     
       7. A method according to  claim 1 , wherein the converted matrix precursor material is an elemental form of tungsten, molybdenum or a combination or alloy of these metals. 
     
     
       8. A method according to  claim 1 , wherein the elemental form of the converted matrix precursor material is nano-grain sized tungsten, molybdenum or a combination or alloy of these metals. 
     
     
       9. A method according to  claim 1 , wherein the ultrahard abrasive particles are suspended in a liquid medium, and a suitable chemical reagent is introduced to form an amorphous or nano-crystalline oxide, hydroxide or oxo-hydroxide entities that bond to the surfaces of the respective particles and build up into coatings on the particles. 
     
     
       10. A method according to  claim 9 , wherein the suitable chemical reagent is at least one alkoxide or solution of the alkoxide(s) in an alcohol. 
     
     
       11. A method according to  claim 9 , wherein the liquid medium is an aliquot of water and alcohol. 
     
     
       12. A method according to  claim 10 , wherein the alkoxide is an alkoxide of an element chosen from aluminium, titanium, silicon, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, hafnium and yttrium. 
     
     
       13. A method according to  claim 10 , wherein two or more alkoxides are introduced into the liquid medium, which are selected from alkoxides of the elements aluminium, titanium, silicon, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, hafnium and yttrium. 
     
     
       14. A method according to  claim 10 , wherein the suitable chemical reagent is a mixed alkoxide compound or complex incorporating two or more of the elements aluminium, titanium, silicon, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, hafnium and yttrium. 
     
     
       15. A method according to  claim 10 , wherein the alcohol has the same alkyl group as the alkoxide(s). 
     
     
       16. A method according to  claim 1 , wherein the matrix precursor material coats are substantially micro-porous. 
     
     
       17. A method according to  claim 16 , wherein the coated ultrahard abrasive particles are subjected to temperature controlled heating in air, vacuum or inert gas to remove volatiles and unwanted chemical species attached to the high surface area of the micro-porous, amorphous coats. 
     
     
       18. A method according to  claim 17 , wherein the coated ultrahard abrasive particles are subjected to further heat treatment or calcination to crystallize the coats to form fine grained or nano-size grained oxide ceramics. 
     
     
       19. A method according to  claim 17 , wherein the coated ultrahard abrasive particles are subjected to further heat treatment to vitrify the coats to form glasses. 
     
     
       20. A method according to  claim 16 , wherein the coated ultrahard abrasive particles are subjected to temperature controlled reactions in reactive gases to convert the coat materials into non-oxide ceramics or glasses. 
     
     
       21. A method according to  claim 20 , wherein nitrides are formed by reacting the coats with ammonia gas. 
     
     
       22. A method according to  claim 20 , wherein carbides are formed by reacting the coats in mixtures of carbonaceous gases and hydrogen. 
     
     
       23. A method according to  claim 22 , wherein the carbides are formed by reacting the coats in a mixture of methane or ethane and hydrogen. 
     
     
       24. A method according to  claim 16 , wherein the coated ultrahard abrasive particles are subjected to temperature controlled reactions in reactive gases to convert the coat materials into oxynitride or oxycarbide ceramics or glasses. 
     
     
       25. A method according to  claim 18 , wherein the oxide coats are reducible by hydrogen and are converted into micro or nano-grain sized elements or metals. 
     
     
       26. A method according to  claim 1 , wherein the coated ultrahard abrasive particles are consolidated, compacted and the coats sintered by hot pressing. 
     
     
       27. A method according to  claim 1 , wherein the coated ultrahard abrasive particles are consolidated, compacted and sintered under conditions of high pressure and temperature. 
     
     
       28. A polycrystalline ultrahard abrasive element comprising diamond of sub-micron or nano size in a matrix selected from titania, TiO 2 , hafnia, HfO 2 , silica, SiO 2 , zirconia, ZrO 2 , titanium nitride, TiN, vanadium nitride, VN, hafnium nitride, HfN, niobium nitrides, NbN, Nb 2 N, tantalum nitride, TaN, molybdenum nitride, Mo 2 N, tungsten nitride, W 2 N, titanium carbide, TiC, vanadium carbide, VC, hafnium carbide, HfC, niobium carbide, NbC, tantalum carbide, TaC, molybdenum carbide, Mo 2 C, tungsten carbides, W 2 C, WC, molybdenum, Mo and Tungsten, W. 
     
     
       29. A polycrystalline ultrahard abrasive element comprising cubic boron nitride of sub-micron or nano size in a matrix selected from alumina, Al 2 O 3 , titania, TiO 2 , hafnia, HfO 2 , silica, SiO 2 , zirconia, ZrO 2 , vanadium nitride, VN, hafnium nitride, HfN, niobium nitrides, NbN, Nb 2 N, tantalum nitride, TaN, molybdenum nitride, Mo 2 N, tungsten nitride, W 2 N, vanadium carbide, VC, hafnium carbide HfC, niobium carbide, NbC, tantalum carbide, TaC, molybdenum carbide, Mo 2 C, tungsten carbides, W 2 C, WC, molybdenum, Mo and Tungsten, W. 
     
     
       30. A polycrystalline ultrahard abrasive element comprising a combination of diamond and cubic boron nitride of sub-micron or nano size in a matrix selected from alumina, Al 2 O 3 , titania, TiO 2 , hafnia, HfO 2 , silica, SiO 2 , zirconia, ZrO 2 , titanium nitride, TiN, vanadium nitride, VN, hafnium nitride, HfN, niobium nitrides, NbN, Nb 2 N, tantalum nitride, TaN, molybdenum nitride, Mo 2 N, tungsten nitride, W 2 N, titanium carbide, TiC, vanadium carbide, VC, hafnium carbide HfC, niobium carbide, NbC, tantalum carbide, TaC, molybdenum carbide, Mo 2 C, tungsten carbides, W 2 C, WC, molybdenum, Mo and Tungsten, W. 
     
     
       31. A polycrystalline ultrahard abrasive element comprising diamond of sub-micron or nano size in an alumina matrix, cubic boron nitride of sub-micron or nano size in a titanium nitride matrix or cubic boron nitride of sub-micron or nano size in a titanium carbide matrix, provided that the grain size of the matrix material is nano-sized. 
     
     
       32. A polycrystalline ultrahard abrasive element according to  claim 28 , wherein the matrix material is non-stoichiometric. 
     
     
       33. A polycrystalline ultrahard abrasive element according to  claim 29 , wherein the matrix material is non-stoichiometric. 
     
     
       34. A polycrystalline ultrahard abrasive element according to  claim 30 , wherein the matrix material is non-stoichiometric. 
     
     
       35. A polycrystalline ultrahard abrasive element according to  claim 31 , wherein the matrix material is non-stoichiometric. 
     
     
       36. The method according to  claim 1 , wherein the step of heating the coated ultrahard abrasive particles is a gaseous environment comprises heating the particles in a gaseous environment incorporating reaction gases to convert the coating. 
     
     
       37. The method according to  claim 1 , wherein the step of consolidating and sintering the coated ultrahard abrasive particles at a pressure and temperature at which the particles are crystallographically or thermodynamically stable comprises generating a polycrystalline abrasive element comprising ultrahard abrasive particles or grains of sub-micron or nano-size in the matrix material, the sintered matrix material being nano-grain sized.